System and method for automatically adjusting a lens power through gaze tracking

ABSTRACT

The present invention relates to a device containing an automatic zoom lens, and more particularly to a zoom lens that is controlled by a processor that is linked to a gaze tracking system. As a user looks onto an object through the device, the gaze tracking system collects data relating to the position of each eye of the user. This eye position data is input into the processor where the focal point of the user is determined. The processor then adjusts the zoom lens to zoom in or out onto the object based on either a predetermined or user input zoom factor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system that changes the magnificationfactor of an optical device based on the point of focus of a user, andmore particularly to a system that changes the magnification factor bydetermining the intersection of gaze lines of the user.

2. Description of the Related Art

Optical devices such as binoculars and cameras often contain systemsthat can zoom in and zoom out to adjust the magnification of a viewedobject. The systems incorporated into these devices change themagnification factor or zoom ratio by moving the zoom lens by eithermanual adjustment or by a motor. The motorized systems typicallyincorporate a dial or push button system or some other electroniccontrol linked to the motor, such as a stepper motor, that moves thelenses to adjust the zoom ratio. By the push of a button a signal issent to a control unit that activates the stepper motor. The steppermotor is mechanically linked to the lens system and adjusts the lensesto zoom in or zoom out at the control of the user. One particularmanufacturer of motorized zoom lenses is Pelco, the operations andspecifications of which can be viewed at their web site<<http://www.pelco.com>>.

One problem of the existing motorized zoom lenses is that they allrequire the use of the hands of the user to control the zoom.

In a different field that is also related to the present invention,there are various techniques for tracking the direction of movement ofthe human eye, generally referred to as gaze tracking. Gaze trackingconcerns detection or measurement of the angular movement and positionof the eye. A document that describes various known gaze trackingtechniques is Eye Controlled Media: Present and Future State, by TheoEngell-Nielsen and Arne John Glenstrup (1995), which may be found at<http://www.diku.dk/˜panic/eyegaze>>, and is hereby incorporated hereinby reference. The various techniques determine the focal point of a userby tracking the movements of the head and/or eyes of the user. Themovement of an eye can be detected by use of the three present daytechniques: detecting reflected light off of different parts of the eye,measuring electric potential differences of the adjacent skin as the eyemoves, and utilizing specially designed contact lenses.

Commercially available gaze tracking systems determine the directionthat a person is looking and then use the data regarding the gaze anglefor a related purpose. For example, certain gaze tracking systemscontrol the movement of a cursor on a computer screen based on where theperson is looking. One manufacturer of gaze tracking systems isSensoMotoric Instruments, and their commercially available equipment maybe seen at <<http://www.smi.de>>. By mounting detectors, e.g. camerasand/or other sensors, onto or near the eyes of a user, the systemdetects the small angular movements of the eye and moves the cursorbased on the angular movement of the eye. The SensoMotoric Instrumentsystems also disclose analysis of detected eye movement for medicaldiagnostic purposes.

Thus, gaze tracking systems have heretofore been limited in theirapplications to analysis of eye movement itself or to the simpleapplication of moving a cursor such that it corresponds to the detectedgaze angle of the eye.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a method and systemfor controlling a magnification factor of an optical device through useof a gaze tracking system.

It is another aspect of the present invention to additionallyincorporate a voice recognition system to control basic functions of thezoom lens.

The invention comprises an optical device having a gaze tracking systemthat automatically adjusts an optical parameter based on a gaze distanceparameter calculated using the gaze angle received from the gazetracking system.

In one embodiment of the invention, an optical device comprises at leastone adjustable optical element, gaze tracking input sensors, a motorthat interfaces with the at least one optical element and is able tomove the at least one element, and a control unit that supports gazetracking and related gaze distance algorithms, as well as software thatprovides control input to the motor. The gaze tracking input sensorsreceive input regarding the gaze angle of the eyes, which is transmittedto the control unit. Gaze tracking algorithm in the control unitdetermines the gaze angle of the eyes, and gaze distance algorithm usethe calculated gaze angle to calculate the gaze distance, that is, thedistance from the viewer to the point where the eyes are focused orgazing. The calculated distance is then used to calculate an adjustmentof the at least one optical element, and a control signal is sent to themotor to make the adjustment in position of the at least one opticalelement.

In another preferred embodiment, a pair of binoculars comprises zoomlenses, one or more gaze tracking cameras, a stepper motor thatinterfaces with the zoom lenses, and a control unit that supports gazetracking and related gaze distance algorithms, as well as software thatprovides control input to the stepper motor. The gaze tracking camerascapture images of the position of one or more features of the eyes thatis used by the gaze tracking algorithms in the control unit to determinethe gaze angle of the eyes. The gaze angle is further processed by thegaze distance algorithm to determine the gaze distance. The gazedistance is further used to determine the appropriate position of thezoom lenses to focus at the gaze distance, and an appropriate controlsignal is provided by the processor to the stepper motor to move thezoom lenses to that position.

In yet another preferred embodiment, a camera comprises a zoom lens, oneor more gaze tracking cameras, a stepper motor that interfaces with thezoom lens, and a control unit that supports gaze tracking and relatedgaze distance algorithms, as well as software that provides controlinput to the stepper motor. The gaze tracking cameras capture images ofthe position of one or more features of the eyes that is used by thegaze tracking algorithm in the control unit to determine the gaze angleof the eyes. The gaze angle is further processed by the gaze distancealgorithm to determine the gaze distance. The gaze distance is furtherused to determine the appropriate position of the zoom lens to focus thecamera at the gaze distance, and an appropriate control signal isprovided by the processor to the stepper motor to move the zoom lens tothat position.

Thus, among other things, the present invention provides an automaticadjustment to the optical element based on the gaze angle andcorresponding focus point of the user. In addition, the presentinvention may additionally incorporate a voice recognition systemwhereby a voice command is required as input before the automaticadjustment is undertaken. For example, a voice command may be requiredbefore the gaze tracking algorithm and the subsequent processing andcontrol of the optical element or lenses will be initiated.Alternatively, such processing may be engaged and running, but the finalcontrol command to the motor requires a voice input.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a diagram of a system for automatically zooming a lensaccording to an embodiment of the present invention;

FIG. 1A is a diagram depicting several elements of a human eye;

FIG. 1B is a side view of a human eye shown in FIG. 1A;

FIG. 1C is a diagram of an image of a human eye captured by a gazetracking system;

FIG. 1D is a diagram of an image of a human eye in a different positionthan in FIG. 1C;

FIG. 2 is a geometric diagram of the system described in FIG. 1according to an embodiment of the present invention; and

FIG. 3 is a flow chart showing the operation of the system according toan embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION

Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the followingdescription, well-known functions or constructions are not described indetail since they would obscure the invention in unnecessary detail.

FIG. 1 shows a user looking through an embodiment of the invention thatcomprises a binocular system 10. As shown in FIG. 1, a gaze trackingsub-system is comprised of two cameras, C1 and C2, a control unit 100and related software stored therein. Eyes E1 and E2 of the user areshown. Also shown are monocular B1 and monocular B2, which make up thebinoculars. A stepper motor 105 is shown connected to zoom lenses Z1 andZ2. As described further below, control unit 100 includes software thatgenerates control signals for control unit 100.

Control unit 100 may comprise, for example, a processor havingassociated RAM and ROM that is mounted directly to the binocular system10, that is interconnected with wires (not shown) to cameras C1, C2 toreceive gaze tracking information data therefrom. Control unit 100 isalso interconnected with a wire or wires (not shown) with stepper motor105 to provide commands thereto and receive position data of the zoomlens. Alternatively, control unit 100 may comprise a separate unit notmounted to the binoculars that is interconnected with the cameras C1, C2and stepper motor 105 with a wire or wireless connection.

Cameras C1, C2 provide video data relating to the angular movement ofthe eyes E1, E2 (gaze tracking data) to the control unit 100. The gazetracking data comports with one of the gaze tracking techniques as knownin the art and which is stored in the form of a gaze tracking algorithmin software of control unit 100. The control unit 100 thus processes thereceived gaze tracking data to determine a gaze angle(s) with respect tonormal (i.e., the axis when the person is looking straight ahead or,equivalently, along the axis of the monoculars B1, B2). The gaze angledetermined is used by the control unit 100, along with other input, suchas the separation of the eyes E1, E2 of the user, to calculate thedistance to the point (for example, point O shown in FIG. 1) that theuser is focused on (the focal distance of the user). The distancebetween the eyes may be provided as a separate input to the control unit100. For example, when the monoculars B1, B1 are adjusted to a viewer'seyes, the eyes are generally aligned with the central axis of eachmonocular. Thus, the distance between the viewer's eyes is substantiallyequal to the separation of the central axes of the monoculars, which isa function of the setting of the adjustment mechanism between themonoculars B1, B2. A sensor that interfaces with the adjustmentmechanism between monoculars B1, B2 may provide the control unit 100with a measure of the adjustment setting between the monoculars B1, B2.The control unit 100 may thus determine the eye separation using, forexample, a table that provides the distance between the central anglesof the monoculars (and thus the viewer's eyes) as a function of thesetting of the adjustment mechanism.

Alternatively, the image provided by the cameras C1, C2 may be used inan analogous manner. For example, in an eye measurement mode, monocularsB1, B2 may be adjusted such that each eye is centered in the imageprovided by the respective camera C1, C2. The control unit 100 has apre-stored table that gives eye separation distance as a function of thesetting of the adjustment mechanism between the monoculars B1, B2 whenthe eyes are so centered in the image. The adjustment setting is sent tothe control unit 100 when the eyes are centered in the image by a sensorthat interfaces with the adjustment mechanism. The control unit 100 usesthe measurement to look up the eye separation distance.

As noted, control unit 100 stores in memory the current position oflenses Z1, Z2. The control unit may keep track of the lens position bymaintaining a count of the number of steps and direction of steps by thestepper motor 105 (referred to as “zoom ticks”) over time.Alternatively, a sensor that interfaces with the stepper motor and/orthe lenses may be queried by the control unit 100 to provide currentposition of the lenses to the control unit 100. After calculating thefocal distance of the user based on the gaze tracking data, control unit100 then determines the position to which the zoom lenses Z1, Z2 must bemoved to provide a zoom focus on the focal point by the binoculars. Thecontrol unit 100 outputs step or zoom tick commands to the stepper motor105 that move the lenses Z1, Z2 from the current position to the userfocal distance. Thus, the binoculars automatically focus to the distanceand thus the point at which the user is gazing.

FIG. 1A depicts a front view of a user's eye E1, having a white scleraportion 200, a (typically) darker iris portion 202 and a central pupilportion 204. The eye in FIG. 1A is shown centered, for example, when thehead is level and the eye is looking at the level horizon along an axis,referred to as the central axis of the user. Thus, for FIG. 1A, thecentral axis of the user is straight out of the page. FIG. 1B is a sideview of the eye that shows a second perspective of the central axis ofthe user.

As noted above, for gaze tracking, a camera, such as camera C1 of FIG.1, provides images of eye E1, such as that shown in FIG. 1A, to controlunit 100 for processing. As known in the art, the images of the eye arecaptured by camera C1 on pixels of a CCD array. Each pixel of the CCDarray thus provides an intensity measurement for the correspondingportion of the captured image to the control unit. Referring back toFIG. 1A, the pixels in the region of the image corresponding to point A(or any point on the border between the sclera portion 200 and the irisportion 202) will show a relatively great change in intensity betweencertain pixels. The same occurs for the pixels corresponding to point B(or any point on the border between the iris portion 202 and the pupil204).

In addition, the control unit may determine a reference point, such aspoint C between the eye and the skin of the user's face 206. Point C maybe detected, for example, by a change in intensity between the pixels ofthe sclera portion 200 and the user's skin 206. Point C is a fixedreference point on the user's head with respect to movement of the eye.The reference point C may be located at other points on the user's headwithin the field of view of the camera, and other points may be used todetermine motion in two dimensions, as described below. The fixedreference point may also be a series of points, determined, for example,by an image recognition algorithm of a human head.

In one technique of gaze tracking, the position of the eye with respectto the head is determined from the image. The principle of this gazetracking technique is described with respect to FIGS. 1C and 1D. FIGS.1C and 1D show two different images of the eye E1 at different gazeangles as recorded by camera C1 and sent to control unit in the form ofdigitized data from each pixel in the camera's CCD. FIG. 1C representsthe eye looking straight ahead, i.e., along the central axis as definedabove. Using the change in intensity between the iris portion 202,sclera portion 200 and the skin of the user's head 206 as describedabove, the control unit 100 determines points A (at the border of theiris portion 202 and the sclera portion 200) and point C (at the borderof the sclera portion 200 and the skin 200) along the X axis as shown.Thus, the image distance X1 is determined by the control unit 100.

In FIG. 1D, the eye is gazing to the left (along the X axis) at a gazeangle with respect to the central axis. Thus, the point A in the imagemoves toward the point C as shown. By determining the positions ofpoints A and C in the image of FIG. 1D (once again, by detecting thechange in intensities between features of the eyes), the control unit100 determines the distance X2.

The gaze angle of the eye E1 with respect to the central axis is afunction of the change in X position, namely X1-X2. The function may bedetermined by the control unit 100 in a training program wheredisplacement of the eye in the images (for example, as measured betweenpoints A and C) is detected and recorded for known gaze angles. (In thesystem of FIG. 1, for example, the gaze angle is zero where the eye iscentered in the image, and the gaze angle is equal to the angular widthof the monocular when gazing at the edge of the field of view. Bycapturing these two images in a training program, the control unit 100may determine a linear correlation between displacement and gaze angle.)Using the data collected in the training program, the control unit 100may extrapolate a gaze angle for a detected displacement in an image(such as X1-X2).

It is noted that the eye need not gaze along the X axis of the image asshown in FIG. 1D, but can lie at some angle with respect to the X and Yaxis. The control unit 100 may have analogous processing thataccommodates movement of the eye in both the X and Y direction (i.e., atany direction in the X-Y plane).

As known in the art, this and other techniques of gaze tracking havebecome highly sophisticated, in order to accommodate movement of thehead, high resolution of small movements, fast response time, movementof the eye in two dimensions, etc. Typically, gaze tracking systems usehigh speed images in processing a gaze angle in order to accommodatethese other variables and factors. In addition, a gaze angle for botheyes is determined. The following documents related to techniques ofgaze tracking are hereby incorporated by reference: 1) U.S. Pat. No.5,861,940 entitled “Eye Detection System For Providing Eye GazeTracking” to Robinson et al.; 2) U.S. Pat. No. 6,152,563 entitled “EyeGaze Direction Tracker” to Hutchinson et al.; 3) Stiefelhagen, Yang &Waibel, A Model-Based Gaze Tracking System, International Journal ofArtificial Intelligence Tools, Vol. 6, No. 2, pp 193-209 (1997); 4)Shumeet Baluja & Dean Pomerleau, “Non-intrusive Gaze Tracking UsingArtificial Neural Networks”, CMU Technical Report, CMU-CS-94-102; 5)Robert J. K. Jacob, “The Use Of Eye Movements In Human-ComputerInteraction Techniques: What You Look At Is What You Get”, ACMTransactions On Information Systems, Vol. 9, No. 3, pp 152-169 (April1991); 6) Heinzmann and Zelinsky, “3-D Facial Pose And Gaze PointEstimation Using A Robust Real-Time Tracking Paradigm”, Proceedings ofthe Third International Conference on Automatic Face and GestureRecognition, sponsored by IEEE Computer Society Technical Committee onPattern Analysis and Machine Intelligence, Apr. 14-16, 1998 (Nara,Japan), pp 142-147.

Alternatively, a commercially available system such as the SensoMotoricInstruments “EyeLink Gaze Tracking” system may be used. (As noted above,details regarding the Eyelink system and other systems of SensoMotoricInstruments may be found on their website, www.smi.de.) The Eyelinksystem provides the cameras and gaze tracking software, however, thesoftware controls movement of a cursor on a display screen in responseto the detected eye movement. Thus, if the Eyelink system is used, forexample, it is adapted with a software subroutine that translates cursorposition (output by the Eyelink gaze tracking system) back to angularposition with respect to the central axis. Such a subroutine can bebased on straightforward geometric and spatial relationships between adisplay and the user.

Thus, whatever gaze tracking technique is used by the binocular system10 of FIG. 1, the gaze tracking components (i.e., cameras C1, C2,control unit 100 and related software) fundamentally calculate a gazeangle of the eyes E1, E2 with respect to the central angle of theviewer. FIG. 2 represents eyes E1, E2 focusing or gazing at a point O inthe distance. As represented in FIG. 2, eyes E1, E2 have gaze angles α1and α2, respectively from axes P1 and P2, respectively. (Axes P1 and P2represent central axes of eyes E1, E2, respectively.) FIG. 2 omitsmonoculars Z1, Z2 shown in FIG. 1 interposed between the viewer's eyesE1, E2 and point O. However, even with the monoculars interposed, theeyes E1, E2 gaze at angles α1, α2 at a virtual point O at a virtualdistance D, as one skilled in the art of optics will readily recognize.

Also shown is distance De the distance between eyes E1 and E2. As notedabove, distance De is known to the control unit 100, for example, bymeasuring the eye separation of a user or otherwise detecting the eyeseparation of the user as described above. Lines P1, P2 and D are linesperpendicular to the line connecting eyes E1 and E2. Once the controlunit 100 calculates the gaze tracking angles α1 and α2 as describedabove, distance D is calculated to the first order by control unit 100as follows: $\begin{matrix}{D = \frac{De}{{\tan \quad {\alpha 1}} + {\tan \quad \alpha \quad 2}}} & {{Eq}.\quad 1}\end{matrix}$

The control unit may use a look up table or a subroutine to calculatethe tangents.

Once distance D is determined, the control unit 100 controls the steppermotor 105 to adjust the position of the zoom lenses Z1, Z2 so that thereis an automatic zoom focus of the default distance d₀. The zoom focallength f corresponding to the default distance d₀ may be calculated as:$\begin{matrix}{f = {\frac{D}{d_{0}}f_{h}}} & {{Eq}.\quad 2}\end{matrix}$

where do is a default zoom distance at which the object will appear,f_(h) is the focal length of the user's (human) optical system. Oncecalculated, the control unit 100 sends control signals to the steppermotor 105 to move the zoom lenses Z1, Z2 such that the optical systemhas focal length f. The actual position is a function of the optics ofthe system; a look-up table of zoom lens position versus focal length ofthe particular optical system may be programmed into the control unit100.

The control unit 100 can further move the zoom lenses Z1, Z2 so that theobject focused on by the viewer at the distance D is zoomed in or out byadditional increments with respect to the initial default zoom distance.The user may input the incremental distances in a calibration processthat relates the additional increments to camera focal length. Oncecalibrated, the zoom increments correspond to a “zoom tick” or step ofthe stepper motor 105 as described above. The relation between focallengths f and zoom ticks z is given, for example, by: $\begin{matrix}{f = \frac{f_{0}}{1 + {a_{0}z} + {a_{1}z^{2}}}} & {{Eq}.\quad 3}\end{matrix}$

where a₀, a₁, and f₀. are calibration parameters that can be provided tothe user to provide a calibration per zoom tick. The focal lengthscorresponding to zoom ticks over the range of movement of the lenses Z1,Z2 may be stored in a look-up table in the control unit 100, forexample. Alternatively, the look-up table may correlate the zoom tick tothe position of lenses Z1, Z2 (the “zoom tick position”) that providesthe corresponding focal length in the optical system.

The zoom ticks provide a way for the user to provide additional zoomingor fine adjustment after the lenses Z1, Z2 are automatically moved suchthat the object gazed upon at distance D is zoomed to the defaultdistance do. A zoom tick input corresponding to a zoom inward or a zoomoutward instructs the control unit 100 to move the lenses Z1, Z2 to thenext zoom tick position either inward or outward. The control unit 100uses the look-up table to determine the adjacent zoom tick positioneither inward or outward to the current position of the lenses Z1, Z2(i.e., the position corresponding to default distance d₀) The controlunit 100 provides the stepper motor 105 to move the lenses Z1, Z2 to thezoom tick position.

After the lenses Z1, Z2 have been moved to focus at the default distanced₀, a zoom tick may be input to the system by the user manually using abutton or alternatively via a voice input. In the latter case, amicrophone is included on the binocular system 10 that interfaces withthe control unit 100. Control unit 100 may have voice recognitionsoftware that recognizes, for example, the word “zoom in” or “zoom out”.Each time the user says “zoom in”, for example, the control unit 100moves the lenses Z1, Z2 inward to the next zoom tick position. Each timethe user says “zoom out”, the control unit 100 moves the lenses Z1, Z2outward to the next zoom tick position. In addition, the initialautomatic zooming of the object gazed upon at distance D to the defaultzoom distance d₀ may first require a user input, such as the spoken word“zoom”. Subsequent fine tuning of the default zoom, or further zoomingin or out for other reasons in zoom tick increments may be undertakenusing the “zoom in” or “zoom out” commands described above.

In addition, such a voice recognition feature may be used in alternativemanners with the binocular system 10 of FIG. 1. For example, the voicerecognition software may recognize spoken numbers and the words “feet”,“meters” or other dimensions. Thus, the control unit 100 recognizes adesired zoom distance spoken by the user, such as “ten feet”. Thecontrol unit 100 uses the same equation given above, namely:$\begin{matrix}{f = {\frac{D}{d}f_{h}}} & {{Eq}.\quad 4}\end{matrix}$

where D represents the gaze distance of the object as before and drefers to the spoken zoom distance desired by the user, in this example,ten feet. Control unit 100 determines the corresponding focal length fusing the above equation and then determines the position of lenses Z1,Z2 corresponding to the focal distance (using, for example, a look-uptable that correlates focal length of the optical system to lensposition). Once the control unit 100 determines the corresponding lensposition, it provides control signals to the stepper motor 105 to movethe lenses to the position, thus zooming the object to ten feet, forexample. Such a feature may be in addition to the automatic defaultzooming and/or zoom tick zooming described above.

The processing by control unit 100 of a comprehensive embodiment of theabove-described binocular system 10 is thus described with reference toFIG. 3 (referring to components and distances as shown in FIGS. 1 and 2)as follows. In step he gaze tracking and voice recognition system isinitialized. This step may include, for example, detecting anddetermining distance between the eyes De. Control unit 100 receivesimage data of the eyes E1, E2 from C1 and C2 as the user looks at objectin step 304 and determines gaze angles α1, α2 of eyes E1, E2 using agaze tracking technique in step 306. Using the gaze angles, the controlunit 100 calculates the distance D to the object O in step 308, forexample, using Eq. 1 above.

The control unit then determines whether a default mode is selected bythe user in step 309. If yes, control unit 100 in step 310 thencalculates (using Eq. 2, for example, or via a look-up table) the focallength of the optical system to zoom the object to a default distance d₀and also determines (via a look-up table, for example), the zoom lensposition corresponding to the focal point. (Alternatively, step 310 maycomprise a unified step, for example, a single look-up table thatcorrelates zoom distance to zoom lens position. The default distance domay then be used to directly determine the lens position.) In step 312,control unit determines whether a zoom voice input (for example, thespoken word “zoom”) has been received. If so, in step 314 the controlunit 100 sends control commands to the stepper motor 105 to move lensesto the determined position for the default zoom location.

After zooming the object to the default distance do, the control unit100 determines in step 316 whether a voice command for zoom ticking hasbeen entered. If so (for example, “zoom in” or “zoom out”), the controlunit 100 in step 318 moves the lenses in or out to the next zoom tickposition in the manner described above. After executing step 318 or ifthe determination in step 316 or 312 is “no”, the processing returns tostep 304, thus ensuring that the object gazed upon is the one that iszoomed when a voice command is received.

If it is determined in step 309 that the default zooming mode is notselected, the control unit 100 determines in step 322 whether a voicecommand is input giving a zoom distance d, for example, “ten feet”. Ifso, then in step 324 the control unit 100 uses the input distance d andthe gaze distance D (determined in steps 304-308) to calculate (usingEq. 4, for example, or via a look-up table) the focal length of theoptical system to zoom the object to a input distance d and alsodetermines (via a look-up table, for example), the zoom lens positioncorresponding to the focal point. (Alternatively, step 324 may comprisea unified step, for example, a single look-up table that correlates zoomdistance to zoom lens position. The input distance d may then be used todirectly determine the lens position.) In step 326, control unit 100sends control commands to the stepper motor 105 to move lenses to thedetermined position for the input zoom distance. The processing thencontinues with step 316 for zoom ticking, as described above. (Step 316is also the point where the control unit continues if the determinationin step 322 is “no”.)

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. For example, while the above exemplaryembodiments described the invention in the context of a binocularsystem, one skilled in the art may readily adapt the invention to anyother type of optical system that has a zoom feature, including, forexample, a camera. In addition, the invention is not limited to zooming,but can be applied to any type of optical adjustment, for example,ordinary focusing of a camera, binoculars or other optical system.

What is claimed is:
 1. An optical system comprising at least oneadjustable optical element, a motor that interfaces with the at leastone adjustable optical element to provide adjustment thereto, first andsecond eye position sensors that detect eye position data for a viewer'sfirst and second eye, respectively, a control unit that receivesposition data from the at first and second eye position sensors andprovides control signals to the motor, the control unit including: i)gaze tracking processing that determines gaze angles for each of theviewer's eyes from eye position data provided by the first and secondeye position sensors, ii) gaze distance processing that determines thegaze distance of the viewer using the determined gaze angles, iii)optical element positioning processing that determines an adjustmentposition of the at least one optical element a function of thedetermined gaze distance, the control unit providing control signals tothe motor to move the at least one adjustable optical element to theadjustment position.
 2. The optical system as in claim 1, wherein the atleast one adjustable optical element is at least one lens that providesa focus to a user of the optical system.
 3. The optical system as inclaim 2, wherein the at least one lens is a zoom lens.
 4. The opticalsystem as in claim 1, wherein the first and second eye position sensorsare first and second cameras directed at the first and second eyes,respectively, of the viewer.
 5. The optical system as in claim 4,wherein the eye position data of the first and second eyes detected bythe first and second cameras, respectively, are images of the first andsecond eyes.
 6. The optical system as in claim 5, wherein the gazetracking processing of the control unit determines gaze angle for theeach of the first and second eye using the position of a feature of thefirst and second eyes in the images.
 7. The optical system as in claim6, wherein the gaze distance processing determines the gaze distance Dof the viewer according to the equation D=De/(tan α1=tan α2) wherein Derepresents the distance between the eyes of the user, α1 is the gazeangle of the first eye determined by the control unit and α2 is the gazeangle of the second eye determined by the control unit.
 8. The opticalsystem as in claim 1, wherein the optical element positioning processingdetermines a default distance from the gaze distance of the viewer, theadjustment position of the at least one optical element being a functionof the default distance.
 9. The optical system as in claim 8, whereinthe at least one optical element is a zoom lens, the default distance isa default zoom distance to which the gaze distance is zoomed, theadjustment position being the location of the at least one opticalelement that that zooms an object at the gaze distance to the defaultzoom distance.
 10. The optical system as in claim 9, wherein the controlunit automatically provides control signals to the motor to move the atleast one adjustable optical element to the adjustment position withoutuser input.
 11. The optical system as in claim 10, wherein the controlunit controls the motor to provide a further adjustment of the zoom lensto subsequent zoom tick positions upon detection of a voice command ofthe viewer.
 12. The optical system as in claim 1, wherein the opticalelement positioning processing receives an input distance from theviewer, the adjustment position of the at least one optical elementbeing a function of the input distance.
 13. The optical system as inclaim 12, wherein the at least one optical element is at least one zoomlens, the input distance is a zoom distance to which the user desiresthe gaze distance to be zoomed, the adjustment position being thelocation of the at least one zoom lens that zooms an object at the gazedistance to the input zoom distance.
 14. The optical system as in claim13, wherein the control unit provides control signals to the motor tomove the at least one zoom lens to the location that zooms an object atthe gaze distance to the input zoom distance.
 15. The optical system asin claim 13, wherein the control unit receives the input zoom distancefrom the viewer by voice input.
 16. The optical system as in claim 13,wherein the control unit controls the motor to provide a furtheradjustment of the zoom lens to subsequent zoom tick positions upondetection of a voice command of the viewer.